irqchip: crossbar: Check for premapped crossbar before allocating

If irq_of_parse_and_map is executed twice, the same crossbar is mapped to two
different GIC interrupts. This is completely undesirable. Instead, check
if the requested crossbar event is pre-allocated and provide that GIC
mapping back to caller if already allocated.

Signed-off-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Sricharan R <r.sricharan@ti.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Link: https://lkml.kernel.org/r/1403766634-18543-3-git-send-email-r.sricharan@ti.com
Signed-off-by: Jason Cooper <jason@lakedaemon.net>

drivers/irqchip/irq-crossbar.c

@@ -51,6 +51,17 @@ static inline void crossbar_writeb(int irq_no, int cb_no)
 	writeb(cb_no, cb->crossbar_base + cb->register_offsets[irq_no]);
 }
 
+static inline int get_prev_map_irq(int cb_no)
+{
+	int i;
+
+	for (i = 0; i < cb->int_max; i++)
+		if (cb->irq_map[i] == cb_no)
+			return i;
+
+	return -ENODEV;
+}
+
 static inline int allocate_free_irq(int cb_no)
 {
 	int i;
@@ -88,11 +99,16 @@ static int crossbar_domain_xlate(struct irq_domain *d,
 {
 	unsigned long ret;
 
+	ret = get_prev_map_irq(intspec[1]);
+	if (!IS_ERR_VALUE(ret))
+		goto found;
+
 	ret = allocate_free_irq(intspec[1]);
 
 	if (IS_ERR_VALUE(ret))
 		return ret;
 
+found:
 	*out_hwirq = ret + GIC_IRQ_START;
 	return 0;
 }